The invention relates generally to electronic interconnect devices, and more particularly, to an apparatus and method for connecting contact points on a spherical shaped device to other devices or components.
Conventional integrated circuits, or "chips," are formed from a flat surface semiconductor wafer. The semiconductor wafer is first manufactured in a semiconductor material manufacturing facility and is then provided to a fabrication facility. At the latter facility, several layers are processed onto the semiconductor wafer surface. Once completed, the wafer is then cut into one or more chips and assembled into packages. Although the processed chip includes several layers fabricated thereon, the chip still remains relatively flat.
A fabrication facility is relatively expensive due to the enormous effort and expense required for creating flat silicon wafers and chips. For example, manufacturing the wafers requires several high-precision steps including creating rod-form polycrystalline semiconductor material; precisely cutting ingots from the semiconductor rods; cleaning and drying the cut ingots; manufacturing a large single crystal from the ingots by melting them in a quartz crucible; grinding, etching, and cleaning the surface of the crystal; cutting, lapping and polishing wafers from the crystal; and heat processing the wafers. Moreover, the wafers produced by the above processes typically have many defects which are largely attributable to the difficulty in making a single, highly pure crystal due to the above cutting, grinding and cleaning processes as well as due to the impurities, including oxygen, associated with containers used in forming the crystals. These defects become more and more prevalent as the integrated circuits formed on these wafers become smaller.
Another major problem associated with modern fabrication facilities for flat chips is that they require extensive and expensive equipment. For example, dust-free clean rooms and temperature-controlled manufacturing and storage areas are necessary to prevent the wafers and chips from defecting and warping. Also, these types of fabrication facilities suffer from a relatively inefficient throughput as well as an inefficient use of the silicon. For example, facilities using in-batch manufacturing, where the wafers are processed by lots, must maintain huge inventories to efficiently utilize all the equipment of the facility. Also, because the wafers are round, and the completed chips are rectangular, the peripheral portion of each wafer cannot be used.
Still another problem associated with modern fabrication facilities is that they do not produce chips that are ready to use. Instead, there are many additional steps that must be completed, including cutting and separating the chip from the wafer; assembling the chip to a lead frame which includes wire bonding, plastic or ceramic molding and cutting and forming the leads, positioning the assembled chip onto a printed circuit board; and mounting the assembled chip to the printed circuit board. The cutting and assembly steps introduce many errors and defects due to the precise requirements of such operations. In addition, the positioning and mounting steps are naturally two-dimensional in character, and therefore do not support curved or three dimensional areas.
In co-pending U.S. patent application Ser. No. 08/858,004 filed on May 16, 1997, assigned to the same assignee as the present application and hereby incorporated by reference, a method and apparatus for manufacturing spherical-shaped semiconductor integrated circuits ("spherical ICs") is disclosed. Included in the reference is a description of how spherical ICs can be mounted to each other and/or to a printed circuit board.
For example, referring to FIG. 1, several different spherical ICs 1, 2, 4, 6, 8, 10, 12 are shown. As a finished product, the spherical ICs 1-12 have solder bumps arranged at predefined intervals throughout their surface. The spherical ICs 1-8 can be easily mounted to a circuit board 14, a bottom portion of each spherical IC resting directly on the circuit board. The spherical IC 1 has solder bumps 16 arranged in a relatively small circle so that the spherical IC 1 can be mounted to the flat circuit board 14. The spherical ICs 2, 4 each have a first set of solder bumps 18, 20, respectively, for mounting to the circuit board 14 and a second set of solder bumps 22, 24, respectively, for connecting to each other. The spherical IC 6 has many solder bumps 26. To electrically connect each solder bump 26 to the circuit board 14, the spherical IC 6 is placed into a socket 28. The socket 28 has pads 30 that align with the solder bumps 26 and electrical connections 32 on a bottom surface for connecting the pads to the circuit board 14. The spherical IC 8 has solder bumps 34, 36, the spherical IC 10 has solder bumps 38, 40, and the spherical IC 12 has solder bumps 42, so that the spherical ICs may connect to the board and to each other, as shown.
However, there is often not a one-to-one alignment between the solder bumps of any two different spherical ICs or a spherical IC and a circuit board. Also, the spacing between solder bumps on one spherical IC may be different from the spacing of the solder bumps on another. Therefore, certain solder bumps may not properly align to corresponding bumps on another spherical IC or circuit board. For example, a positive power supply bump on one spherical IC may improperly align with a negative power supply bump on another.